In recent years, devices referred to as metamaterials have been attracting attention. This metamaterial refers to an artificial substance which has electromagnetic and/or optical properties provided by none of substances in nature. Typical properties of this metamaterial include a negative magnetic permeability (μ<0), a negative dielectric constant (∈<0), or a negative refractive index (when the magnetic permeability and the dielectric constant are both negative). It is to be noted that the region with μ<0 and ∈>0 or the region with μ>0 and ∈<0 is also referred to as a “evanescent solution region”, whereas the region with μ<0 and ∈<0 is also referred to as a “left-handed region”.
It is common that the left-handed metamaterial with μ<0 and ∈<0 is created by the combination of a substance with a negative dielectric constant ∈ with a substance with a negative magnetic permeability μ.
As a means for achieving a negative magnetic permeability μ, a split ring resonator (SRR) can be used (for example, see Non-Patent Document 1)
On the other hand, as a means for achieving a negative dielectric constant ∈, a metal rod can be used. In a mainstream method for achieving a negative dielectric constant ∈, a metal rod which has an infinite (that is, sufficiently large with respect to the wavelength of electromagnetic waves) length is used to decrease the plasma frequency. Non-Patent document discloses an array of metal thin wires which allows for the achievement of a negative dielectric constant ∈. In addition, Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-507733) discloses a wire in a periodic lattice for a negative dielectric constant.
In contrast, it has been also known that a metal rod which has a finite length generates a negative dielectric constant. When a metal rod which has a length of half the wavelength λ of electromagnetic waves is resonated with the electromagnetic waves, a negative dielectric constant is generated.    Patent Document 1: Japanese Patent Application Laid-Open No. 2008-507733    Non-Patent document 1: “Left-handed Metamaterial”, Nikkei Electronics January 2, Nikkei Business Publications, Inc., Jan. 2, 2006, PP. 75-81    Non-Patent document 2: J B Pendry et al., “Low Frequency Plasmons in thin-wire structures”, J. Phys. Condens. Matter Vol. 10 (1998) 4785-4809